Soil Engineering Properties (nfm)

Simplified Classification of Soil Deposits

Some Descriptive Soils Names

major division

Principal Soil Type

Pertinent Engineering Characteristics

Argillaceous

Soils predominantly clay or abounding in clays or clay-like materiales

Resi -dual soil

mineral

material formed by disintegration of underlying parent rock or partially indurated material

residual sands and rocks fragment of various sizes formed by solution and leaching of cementing material, leaving the more resistant particles commonly quartz

generally favorable foundation conditions

Red dog

The residue from burned coal dumps

residual clay extremely finely divided clay material formed in place by the weathering of rock, derived either by the chemical decay of felspar and other rock material or by the removal of non clay mineral constituents by solution from a clay bearing rock

variable properties requiring investigation to determine depth and condition of weathering

Micaceous soils

Soil which contains a sufficient amount of mica to

give it distinctive appearance and characteristics.

organic

Accumulations of highly organic material formed in place by the growth & sub- sequent decay of plant life

Peat: A somewhat fibrous aggregate of decayed and decaying vegetable matter having a dark color and odor of decay

Muck: finelly divided, well decomposed organic material intermixed with a high percentage (20 - 50%) of mineral matter.

very compressible. Entirelly unsuitable for supporting building foundations

Topsoil

General term applied to the top centimeters of soil deposit. Usually consider organic matter and are productive of plant life

Trans -ported Soils

alluvial

Material transported and deposited by running waters

Floodplain deposit: unconsolidated soils deposited by a stream within that portion of its valleys subject to inundation by floodwater

Peat

A term which is frequently applied to fibrous, partially decayed organic matter or a soil which contains a large proportion of such materials. Extremely loose and compressible

Natural levees: long, bread, low ridges of sand, silt or silty clay deposited by a stream on its floodplain and along both banks of itschannel during overbank flow

Generally favorable foundation conditions

Alluvium

Deposits of mud, silt and other material commonly found on the flat lands along the lower courses of streams

Point bar: alternating deposits of arcuate ridges and swales (lows) formed on the inside or convex bank of migrating river brends. Ridge deposits consist primarilly of silt and sand swales are clay -filled

Generally favorable foundation con-ditions, detailed investigations are neces -sary to locate discontinuities. Flow sli-des may be a problem along riverbanks

Rock flour

Fine-grained usually sedimentary of low plasticity and cohesion. Particles are usually in the lower range of silts sizes. At high moisture contents, it may become 3quick" under the action of traffic

Channel fill: deposites laid down in abandonned meander loops isolated when rivers shorten their course. Composed primarilly of clay, however silty and sandy soils are found at the upstream and downstream ends

fine grain soils are usually compressible. Portions may be very heterogeneous. Silty soils generally present favorable foundation conditions

Shale

A thinly laminated rock-like material resulting from consolidation of clay under extreme pressure. Some shales revert to clay on exposure to air and moisture

Backswamp: the prolonged accumulation of floodwater sediments in flood basins behing the natural levees of a river. Material are generally clays but tend to become more silty near riverbank

Relatively uniform is a horizontal direction. Clays are usually subjected to seasonal volume changes

Lateritic Soils

Residual tropical soils of many different kind, frequently red, granular structure, low plasticity, good drainability, remolded by water they often become plastic and clayey to the depth disturbed

Terrace deposits: unconsolidated alluvion (including gravel) produced by removal downcutting of the valley flood by a rejuvenated stream

Generally favorable conditions. Usually act subject to flooding

Tufa

A loose porous deposit of calcium carbonate which

usually contains organic remains

Fan deposit:s alluvial deposits at foot of hills or mountains. Extensive plains or alluvial fans

generally favorable foundations conditions

Marl

A soft calcareous deposit mixed with clay, silts and sands often containing shells or organic remains.

Deltaic deposits: deposits formed at the mouths of rivers which result in extension of shoreline

Generally fine-grained and compressible. Many localvariations is soil conditions

Varved clay

Sedimentary deposit which consists of alternate thin layers of silt and clay

Lacus -trine

Material deposited in a lac

Lacustrine deposits: other than associated with glaciation) by waves, currents and organo-chemical processes. Deposits consist of unstratified organic clay or clay in central portions of the lake and typically grade to stratified silts ans sands in peripheral zones

Usually very uniform in horizontal direction. Fine-grained soils generally compressible

Muck, mud

The very soft slimy silt or organic silt which is frequently found on lake or river bottoms

Estua -rine

Material deposited in an estuary

Estuarine deposit: fine-grained sediment (usually silt and clay) of marine and fluvial origin mixed with decomposed organic matter laid down in brackish water of an estuary.

Generally compressible. Many local variations

Aeolism

Material deposited by wind

Loess: as unstratified calcareous deposit consisting predominantly of silt subordinate grain sizes ranging from sand to clay. Often contains fossils and is transversed by a network of small narrow, vertical tubes frequently filled with calcium carbonate conceptions formed by root fibers nowdecayed

relativelly uniform deposit characterized by ability to stand in vertical cuts. Collapsible structure. Deep weathering or saturation can modify characteristics

Loess

silty soil of aeolian origin characterized by a loose porous structure and a natural vertical slope

Dune sands: mounds, ridges and silt of uniform fine sand characteristicall exhibiting rounded grains

Very uniform grain-size, may exist in relativelly loose conditions

Glacial

Material transported and deposited by glaciers or by melt water from glacier

Glacial till: An accumulation of debris, deposited beneath or at the side (lateral moraines) or at the lower limit of the glacier (terminal moraine). Material lowered to ground surface in an irregular sheet by a melting glacier is known as a ground moraine

Material of all sizes in various proportions from boulders and gravel to clay. Deposits are unstratified. Generally favorable foundation ; but rapid change are common

Glacio-fluvial deposits: Coarse and fine-grained material deposited by stream of melt water from glaciers. Material deposited on ground surface beyond terminal of glacier is known as an outwash plain. Gravel ridges known as kames and cakers

Many localvariations. Generally present favorable foundation conditions

Boulder clay

Another name for glacial till

Glacio-lacustrine deposits: Material deposited within lakes by melt water from glaciers. Consisting of clay incentral portions of lake and alternate layers of silty clay or silt and clay (varved clay) in peripheral zones.

Very uniform in an horizontal direction

Marine

Material transported and deposited by ocean waves and currents in shores and offshore area

Shore deposit: of sands and / or gravel formed by the transporting, destructive and sorting action of waves on the shore line

Relatively uniform ans of moderate to high density

Marine clays: organic and inorganic deposits of fine-grained material

Generally very uniform in composition. Compressible and usually very sensitive to remolding

Limerock

Soft friable, compact cream-like, high calcium limestone consisting of coral and other marine remains disintegrated by weathering

Collu -vial

Material transported and deposited by gravity

Talus: deposit created by gradual accumulation of unsorted rock fragment and debris of base of cliffs

Colluvial deposits: Fine colluvium consisting of clayey sand sandy silt or clay

Previous movement indicate possible future difficulties. Generally unstable foundations conditions

Bentonite

Clay of high plasticity formed by the decomposition of volcanic ash; it has a high swelling characteristic

Landside deposits: considerable masses of soil or rock that have slipped down more or less as units, from their former position on steep slopes

Tuff

Applied to compacted deposits of the fine material

materials ejected from volcanoes, such as more or less cemented dust and cinder. Tuffs are more or less stratified and in various states of consolidation

Pyro -clastic

Material ejected by volcanoes and transported by gravity, wind and air

Ejects: loose deposits of volcanic ash, lapilli,bombs, cinders, etc.

Typically shard-like particles of silt size with larger volcanic debris. Weathering and redeposition produce highly plastic compressible clay . Unusual and difficult foundations conditions

Volcanic ash

Uncemented volcanic debris, usually made up of particles less than 4mm in diameter. Upon weathering a volcanic clay of high compressibility is frequently formed. Some volcanic clays present unusually difficult construction problems.

Determination of the Consistency of Clays

Improving performance of collapsible soil

unconfined compressive strength q

Field identification

Consistency

Depth of Soil treatment m

description

< 0.25

easily penetrated by fist

very soft

0 to 1.5 m

wetting, mixing and compaction

0.25 to 0.5

easilly penetrated by thumb

soft

> 1.5 m

overexcavation & recompaction with or without chemical additives such as lime of cement

0.5 to 1.0

can be penetrated by thum with moderate effort

medium

Hydrcompaction

1.0 to 2.0

readily indented by thumb but penetrated only with great effort

stiff

Vibroflotation

2.0 to 4.0

readily indented by thumbnail

very stiff

Lime pressure injection

> 4.0

indented with difficulty by thumbnail

hard

Sodium silicate injection

prewetting by ponding; vertical sand drains promote wetting of subsurface soils

Argillaceous Material

s

s

medium to soft : t

stiff t

hard (clay shale) t

clay stone

silt stone

drain shear strength at natural water content : s

LL: liquid limit; w*: maximum water content due to slaking; Li: liquidity index; ∆Li : change in liquidity index

in terms of amount of Slaking

very low LL > 20

low LL 20 to 50L & S

medium LL 50 to 90

high LL 90 to 140

very high LL > 140

rate of slaking

∆Li

2 hours water immersion

slow ∆Li < 0.75

VL & S

L & S

M & S

H & S

VH & S

fast 0.75 < ∆Li < 1.25

VL & F

L & F

M & F

H & F

VH & F

very fast ∆Li > 1.25

VL & VF

L & VF

M & VF

H & VF

VH & VF